Late Quaternary sediment dispersal and accumulation on slopes of the Great Barrier Reef mixed siliciclastic-carbonate depositional system, Gulf of Papua, Papua New Guinea and North Queensland Margin, Australia

The Great Barrier Reef (GBR) margin, located on the continental margin between Papua New Guinea and northeast Australia, is the largest extant example of a tropical mixed siliciclastic-carbonate depositional system. It is constructed by the combined input of terrigenous siliciclastic sediment delivered through riverine transport and biogenous carbonate sediment from neritic and pelagic production. This study investigates late Quaternary changes in sediment dispersal and accumulation on the slopes of this margin. Sedimentation across the GBR mixed system also serves as an important analog for understanding deposition on other extant and ancient systems and provides insight into global change, geochemical cycling, and resource management. Several concepts (e.g., reciprocal sedimentation, coeval sedimentation) have been proposed to explain spatial and temporal variations in siliciclastic and carbonate components. While these concepts are frequently used to evaluate ancient tropical mixed systems, they are rarely assessed in the Quaternary, an interval where the magnitude and timing of sea level are relatively well-constrained, and precise dating techniques can be used. These studies of the GBR mixed system integrate a full suite of data including core, seismic, and multi-beam bathymetry to gain a quantitative understanding of the GBR system and to evaluate reciprocal sedimentation concepts. Results indicate that slopes along the GBR margin have a complex depositional history. Sea level, climate, and margin physiography are all important depositional controls affecting timing, location, and mechanism of sediment dispersal. Reciprocal sedimentation can be used to predict carbonate accumulation. However, this approach must be combined with a firm understanding of sedimentary controls and processes to accurately predict siliciclastic accumulation along this margin.